The volatilization of scent from a substrate has been described previously. Many materials have been described that release a volatile material, such as a scent, including ceramics, polymers, wood and cellulose materials. Cotton has been used to release volatile materials as described in U.S. Pat. Nos. 2,615,754 and 5,372,303. Fabric has also been described as an absorbent medium from which a volatile material can evaporate as described in U.S. Pat. No. 2,626,833. In U.S. Pat. No. 855,984 a sponge is used to volatilize a perfume or disinfectant. U.S. Pat. No. 1,988,141 describes the use of a felt pad to release a perfume. These materials all produce articles that have a very rapid release of the scent from their matrix if unimproved with further restrictions which add significant cost to the articles.
Wood has been used to hold scent in articles like incense. To release significant quantities of the scent, however, the wooden incense sticks are typically burned. Allowing the incense sticks to release their scent without burning results in an inadequate scent release. Additionally, wood is not highly absorbent and therefore absorbs low amounts of scented material. Wood pulp has been used to absorb fragrance and release it, as described in U.S. Pat. No. 2,120,204. The use of wood pulp poses very restrictive uses because it is quite friable and cannot be made into stable rods that resist breaking. Molded plastics have also been used to disperse scents as described in U.S. Pat. No. 4,802,626. The amount of scent that releases from this type of medium in a reasonable time frame is very limited.
Many air fresheners and volatile material dispersers use paper products as a medium from which a scent may evaporate. Commercial examples of these types of air fresheners use a stiff blotter type paper and are produced by Medo Industries, Baltimore, Md. and Little Trees, Watertown, N.Y. U.S. Pat. No. 6,575,383 describes using 120# commercial blotting paper, beverage board type papers, and commercial Cover Stock to absorb a fragrance for freshening air in a bathroom. U.S. Pat. No. 3,575,345 uses a porous paper such as filter paper. Other paper and blotter-based dispersing devices are found in U.S. Pat. Nos. 5,503,332; 5,395,047; 6,168,088; 6,575,383; and 6,688,551.
The major disadvantage of such paper products is that they have a large surface area to volume ratio, a relatively low density or specific gravity, and they release their volatile material too rapidly for many applications. There are descriptions of devices that modify these materials to slow the release rate of the volatile material off of the medium. These modifications have included coating the paper with an occlusive material like a film-forming chemical or a layer of plastic that has limited porosity or alternatively, placing the paper inside an outer covering thereby restricting the vaporization of the scent. While these modifications have shown some effectiveness in slowing the evaporation rate, the modifications add significant cost to the products and require special manufacturing steps.
There are also existing air fresheners that contain a wick structure absorbing a liquid through the wick. Examples of this type of a system are described in U.S. Patent Application 20020136886 and U.S. Pat. Nos. 4,384,589 and 5,437,410. The disadvantage of these types of devices is the high cost and necessity for multiple components.
What is needed are devices for providing scents that are durable, easily manufactured and provide a slow release of scent for many applications.